All methods, apparatus, and inventions related to the measurement of SV/CO by the electrical bioimpedance method have heretofore been implemented by means of:                Transthoracic method, known as transthoracic electrical bioimpedance cardiography, or impedance cardiography (ICG), U.S. Pat. No. 4,450,527 A.        Transthoracic electrical (bioimpedance) velocimetry, U.S. Pat. No. 6,511,438 B2.        Total or whole body electrical bioimpedance plethysmography method, also known as total (whole) body electrical bioimpedance cardiography, U.S. Pat. Nos. 5,469,859, 5,735,284.        Transbrachial electrical (bioimpedance) velocimetry, U.S. Pat. No. 7,261,697, B2, U.S. Pat. No. 7,740,590 B2, U.S. Pat. No. 7,806,830 B2.        Method and Apparatus for Determination of Left Ventricular Stroke Volume and Cardiac Output Using the Arteries of the Forearm, U.S. Pat. No. 9,451,888 B1        Endotracheal cardiac output, U.S. Pat. Nos. 5,782,774, 6,292,689.        
Apart from the transthoracic and transbrachial velocimetric techniques, all prior methods ascribe a pure volumetric origin for the time-dependent primary impedance change ΔZ(t) (ohm, Ω) and its peak time rate of change (first time-derivative) dZ(t)/dtmax, originally thought to be measured in Ω·s−1. The two most widely used methods ascribing a volumetric (plethysmographic) etiology for both ΔZ(t) and dZ/dtmax include the Nyboer-Kubicek and Sramek-Bernstein techniques, which differ with respect to their individual spot or band-electrode configurations on the thorax (chest) and their respective SV equations (Bernstein et al. Stroke volume equation for impedance cardiography. Med Biol Eng Comput 2005; 43:443-50; Bernstein D P, Impedance Cardiography: Pulsatile blood flow and the biophysical and electrodynamic basis for the stroke volume equations. J Electr Bioimp. 2010; 1:2-7) and as disclosed in Bernstein et al. U.S. Pat. No. 6,511,438 B2).
The aforementioned bioimpedance methods have been implemented for a variety of medical and non-medical purposes:                Determination of CO in sick hospitalized patients.        Cardiac pacemaker resynchronization therapy.        Cardiac rehabilitation for post myocardial infarction and heart failure patients.        Exercise physiology using the transthoracic methods.        Efficacy of intense aerobic training as a surrogate for maximal oxygen consumption.        Effect of medications on the cardiovascular system.        
Studies involving the radial/ulnar arteries of the forearm include:                Nyboer (Nyboer J. Electrical impedance plethysmography; a physical and physiologic approach to peripheral vascular study. Circulation 1950; 2:811-21) demonstrated that electrical impedance changes (ΔZ) of the forearm correlated with volumetric strain gauge approximations of volume changes in the vessels of the forearm.        Wang et al. (Wang et al. Evaluation of changes in cardiac output from electrical impedance changes of the forearm. Physiol Meas. 2007; 28:989-99) and Wang et al. (Wang et al. Development of forearm impedance plethysmography for minimally invasive monitoring of cardiac pumping function. Journal of Biomechanical Science and Engineering. 2011; 14:122-29) demonstrated that, the change in magnitude and percent change in the magnitude of forearm of AZ and the change in magnitude and percent change in area beneath the ΔZ were highly correlated with the change in magnitude and percent change in magnitude of measured stroke volume (SV). Neither the magnitude of ΔZ or area beneath the ΔZ waveform correlated well with measured SV.        Targett et al. (Targett R et al. Simultaneous Doppler blood velocity measurements from the aorta and radial artery in normal human normal subjects. Cardiovasc Res. 1985; 19:394-399) demonstrated that peak radial artery blood acceleration has a constant relationship with peak aortic blood acceleration, regardless of age.        Chemla et al. (Chemla et al. Blood flow acceleration in the carotid and brachial arteries of healthy volunteers: respective contributions of cardiac performance and local resistance. Fundam Clin Pharmacol 1996; 10:393-99) noted that peak brachial artery and peak radial artery acceleration were of similar magnitudes.        Zambanini et al. (Zambanini et al. Wave energy in carotid, brachial and radial arteries: a noninvasive approach using wave intensity analysis. Am J Physiol Heart Circ Physiol. 2005; 289:H270-H276) demonstrated that the magnitude of brachial and radial artery velocities and peak slope of the velocity waveforms were nearly identical.        